The present invention relates to integrated circuit (IC) structures, and more specifically, to antifuses for in line circuit modification.
Fuses and antifuses have been used in integrated circuits for tailoring circuit parameters for optimal performance. Fuses increase the resistance of a circuit path when subjected to a programming current. Fuses typically include a fuse link and contact regions at both ends of the fuse link including a plurality of contacts of a uniformed size. The fuse has an underlying polycrystalline layer formed over a substrate and an overlying silicide layer. Fuses are “blown” by applying a voltage across the fuse structure. This voltage causes a current to flow and the structure to open, resulting in a permanent open circuit. Fuses are structures in which resistance is increased during programming and antifuses are structures in which resistance is decreased during programming.
Antifuses are structures that, when first fabricated, are an open circuit. When the antifuse is “fused,” the open circuit becomes closed and conduction across the antifuse becomes possible. Thus, antifuses are used to perform the opposite function of a fuse. Typically an antifuse is fused by applying a sufficient voltage, called a “fusing voltage” across the antifuse structure. This voltage causes a current to flow and the structure to fuse together, resulting in a permanent electrical connection.
Each contact formed on the contact regions is typically formed by etching a contact via to a surface of the substrate and depositing a metal material such as titanium (Ti) and organic carrier material within the via to the surface of the substrate by a chemical vapor deposition (CVD) process thereby evaporating the organic material and leaving the metal material on the surface of the substrate. This process is performed at a temperature of approximately 400 degrees Celsius. The processing temperature may be too low to completely evaporate the organic material; therefore, the metal material and any residual carbon containing material are then treated by an N2/H2 plasma to break a bond of the metal material and the carbon containing material. During this treatment, hydrogen reacts with the carbon containing material thereby evaporating the residual carbon containing material and the nitrogen reacts with the metal material and leaves a metal precursor which acts a liner within the contact via. Contact material is then deposited within the contact via to form the contact.